Drawing ASTs for expressions: Correct Solution

For each of the Java expressions below:

• Draw an AST for the expression.
• Show how the expression evaluates at each node in the tree.

Be sure that your tree accurately reflects how Java would evaluate the expression.

Part 1

Given the following variables:

int in = 9;
double nauen = 3.0;
int eud = 7;
double flacra = 4.0;

...draw the AST and evaluation results for the following expression:

0 - in * 4 / nauen + 8 + 2 + eud % flacra

Solution

Things to double-check in your solution:

• Do you have the left and right branches on the correct side?
• Did you indicate the difference between ints and floating point values?

Part 2

Given the following variables:

double jirat = 4.0;
int chriwllan = 5;
double serd = 4.0;
double bedte = 2.0;
double uir = 1.0;
int hicbaur = 6;
int en = 8;

...draw the AST and evaluation results for the following expression:

5 <= 8 || 0 >= 2 == jirat >= chriwllan && serd == bedte && uir == 8 || 1 < hicbaur && !(8 != en)

Solution

Things to double-check in your solution:

• Does your tree correctly reflect the precedence of && and ||?
• Did you correctly show short-circuiting? (That is when the right branch of && or || is never evaluated because the left branch already determines the answer.)

Part 3

Draw the AST and evaluation results for the following expression:

0 + 1 + 2 + 3 + (4 + "5" + 6) + 7 + "8"

Solution

Things to double-check in your solution:

• Did you indicate the distinction between ints and Strings?
• Are your left/right branches correct?

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